The invention relates to a discharge apparatus for flowable media having a basic body for receiving a medium reservoir and a thrust piston pump, which has a pump piston displaceably on a piston runway between a starting position and a pump stroke end position, as well as a pump chamber connected to a discharge opening of the apparatus by means of a discharge channel and defined by a pump cylinder optionally forming the medium reservoir and the pump piston.
Such a discharge apparatus is described in U.S. Pat. No. 4,964,069. It protects the pump cylinder and a resilient stop constructed in the manner of a snap locking means cooperating in such a way that prior to the discharge of a partial stroke a specific actuating pressure must be applied by the operator, so that after overcoming this pressure point the discharge of the liquid takes place with a certain minimum force and speed. This construction ensures that e.g. on atomizing the medium the pressure from the first instant is sufficient for atomization purposes and that the pump is actuated up to its end, i.e. performs the complete stroke and the entire content of its medium reservoir, which simultaneously forms the pump cylinder, is discharged in one or two strokes. Such single or double dosing or proportioning devices are advantageous for the dispensing of medicaments, which are particularly critical with respect to proportioning, contamination, preservation or other criteria.
U.S. Pat. No. 5,469,989 and U.S. Continuation-in-part patent application Ser. No. 546,428 thereof discloses the use of medium reservoirs for a single discharge stroke, which are sealed by a plug simultaneously serving as the piston, the plug being perforated by a needle for actuation purposes. The medium reservoir is received in a sleeve, which has external projections and which cooperate with corresponding projections on the inside of a casing basic body in the manner of a snap fastening. On actuation it is firstly necessary to overcome the static friction, before said beads slide on the faces against which they engage, so that a pressure point must be overcome.
In the U.S. patent application Ser. No. 08/594,055 filed concurrently with the present application by the co-inventors Karl-Heinz FUCHS and Stefan RITSCHE there is disclosed a discharge apparatus for flowable media comprising a basic body, at least partly receiving, a pump unit having a pump chamber connectable to a discharge opening via a discharge channel, the pump chamber being bounded by a pump cylinder and a pump piston, the pump cylinder forming the medium reservoir, the pump piston being displaceably guided in the pump cylinder, a tamper-evident closure which can be destroyed by an actuating force, including at least one breakable material bridge between the pump unit and the basic body. This is accomplished on one hand by a ring shaped fastening element which is integral with breakable material bridges on the casing or a pump arrangement or by an increased piercing resistance of a ram which pierces through a piston plug. The ring which may be connected with an actuating sleeve receiving the reservoir can be snapped in at lower projections of the apparatus housing. It further contains the idea to provide the pump arrangement with a second ring connected thereto by breakable bridges in order to provide a tamper-evident limit also for a second stroke.